Heat-developable light-sensitive materials and their processes are described, for example, in Shashin Kogyo no Kiso (published by Corona Co. in 1979), pp. 553 to 555, Eizo Joho (April, 1973), p. 40, Neblette's Handbook of Photography and Reprography, 7th Ed. (published by Van Nostrand Reinhold Company), pp. 32-33, U.S. Pat. Nos. 3,152,904, 3,301,678, 3,392,020, 3,457,075, British Patents 1,131,108, 1,167,777, and Research Disclosure RD No. 17029 (June, 1978), pp. 9-15.
Processes for transferring mobile dyes imagewise formed by heat development to an image receiving layer by heating, and image receiving materials for use therewith, are described in Japanese Patent Application (OPI) Nos. 58543/83 (corresponding to U.S. Pat. No. 4,500,626), 79247/83 (corresponding to U.S. Pat. No. 4,483,914), 168439/84 (corresponding to U.S. Pat. application Ser. No. 509,592 (Mar. 16, 1984)), (the term "OPI" as used herein refers to a "published unexamined Japanese patent application"), etc.
Methods for heating the heat-developable light-sensitive materials or the image receiving materials (hereinafter collectively referred to as photographic materials) include a method of bringing a photographic material into contact with a high heat capacity hot plate, a method of directly heating a photographic material by irradiating with a laser, infrared rays, ultrasonic waves, high frequency waves, etc., and a method of passing a photographic material through a hot gas zone. However, these methods fail to provide fully satisfactory results due to their various defects. For example, with the method of using a hot plate, it takes a long time to uniformly heat the hot plate and, therefore, the method requires a large electrical energy and, when the contact is insufficient, uniform conduction of the heat to the photographic material is difficult. With the method of using radiation such as a laser, a large sized equipment required makes it difficult to build a compact system, and the method of utilizing gas has the defect that it takes a long time due to the small heat capacity of gas.
In order to overcome these defects, a process of using an electrically conductive heating element layer in combination with a heat-developable light-sensitive layer has been described in Japanese Patent Application (OPI) No. 66442/73 (corresponding to U.S. patent application Ser. No. 206,368), etc. However, since this electronically conductive heating element layer is formed by coating an organic solvent solution, explosion-proof equipment is required for the coating process, and hence this process has defects with respect to safety, economic aspects, and practical workability.
In addition, the inventors have previously invented a heat-developable light-sensitive material having an electrically conductive layer wherein a conductivity imparting substance is dispersed in a hydrophilic binder as described in Japanese Patent Application (OPI) No. 120356/85 and Japanese Patent Application No. 151815/84 (corresponding to U.S. patent application Ser. No. 757,556 (July 22, 1985)).
However, these conventional conductive layers undergo serious changes in their electric resistance when the ambient humidity varies. Therefore, there arises a problem that, when humidity varies, the density of an image formed by heat development or a heat transfer process fluctuates. Of course, this problem can be solved to some extent by changing energizing conditions, but it is quite troublesome to change energizing conditions depending upon ambient humidity, and, in some cases, fluctuation of the resistance value exceeds the scope within which energizing control can be effective. Thus, the controlled energizing technique cannot be a sufficient solution for the above described problem.